U.S. patent number 7,648,909 [Application Number 11/321,533] was granted by the patent office on 2010-01-19 for method for fabricating semiconductor device with metal line.
This patent grant is currently assigned to Hynix Semiconductor, Inc.. Invention is credited to Sang-Hoon Cho, Suk-Ki Kim, Hae-Jung Lee.
United States Patent |
7,648,909 |
Lee , et al. |
January 19, 2010 |
Method for fabricating semiconductor device with metal line
Abstract
A method for fabricating a semiconductor device includes forming
an inter-layer insulation layer on a substrate; forming openings in
the inter-layer insulation layer; forming a metal barrier layer in
the openings and on the inter-layer insulation layer; forming a
first conductive layer on the metal barrier layer and filled in the
openings; etching the first conductive layer to form
interconnection layers in the openings and to expose portions of
the metal barrier layer, the interconnection layers being inside
the openings and at a depth from a top of the openings; etching the
exposed portions of the metal barrier layer to obtain a sloped
profile of the metal barrier layer at top lateral portions of the
openings; forming a second conductive layer over the inter-layer
insulation layer, the interconnection layers and the metal barrier
layer with the sloped profile; and patterning the second conductive
layer to form metal lines.
Inventors: |
Lee; Hae-Jung (Ichon-shi,
KR), Cho; Sang-Hoon (Ichon-shi, KR), Kim;
Suk-Ki (Ichon-shi, KR) |
Assignee: |
Hynix Semiconductor, Inc.
(Gyeonggi-do, KR)
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Family
ID: |
37195461 |
Appl.
No.: |
11/321,533 |
Filed: |
December 30, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060246708 A1 |
Nov 2, 2006 |
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Foreign Application Priority Data
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Apr 30, 2005 [KR] |
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10-2005-0036591 |
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Current U.S.
Class: |
438/640;
257/E21.578 |
Current CPC
Class: |
H01L
21/32136 (20130101); H01L 21/76877 (20130101); H01L
21/76849 (20130101); H01L 21/76843 (20130101); H01L
21/32115 (20130101) |
Current International
Class: |
H01L
21/4763 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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04-225549 |
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Aug 1992 |
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JP |
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07-294280 |
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Nov 1995 |
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JP |
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11-040668 |
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Feb 1999 |
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JP |
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11-097536 |
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Apr 1999 |
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JP |
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2003-303882 |
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Oct 2003 |
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JP |
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2003303882 |
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Oct 2003 |
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JP |
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550642 |
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Sep 2003 |
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TW |
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Other References
Bestwick et al. "Tungsten etching mechanisms in CF4/O2 reactive ion
etching plasmas" J. Appl. Phys. 66 (10), Nov. 15, 1989. cited by
examiner .
Notice of Search Report from the Taiwanese Patent Office, dated
Feb. 8, 2007, in counterpart Taiwanese Patent Application No.
94146972. cited by other .
English-language translation of the First Office Action from the
State Intellectual Property Office dated Jul. 20, 2007, in
counterpart Chinese Patent Application No. 200510097536.0. cited by
other.
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Primary Examiner: Smith; Matthew
Assistant Examiner: Scarlett; Shaka
Attorney, Agent or Firm: IP & T Law Firm PLC
Claims
What is claimed is:
1. A method for fabricating a semiconductor device, comprising:
forming an inter-layer insulation layer on a substrate; forming
openings in the inter-layer insulation layer; forming a metal
barrier layer in the openings and on the inter-layer insulation
layer; forming a first conductive layer on the metal barrier layer
and filled in the openings; performing a first etching process to
etch the first conductive layer to form interconnection layers in
the openings, wherein the interconnection layers are formed
completely inside the openings and at a depth from a top of the
openings; performing a second etching process on portions of the
metal barrier layer exposed after the first etching process to
obtain a sloped profile of the metal barrier layer at top lateral
portions of the openings, the sloped profile of the metal barrier
having a rounded cusp; forming a second conductive layer over the
inter-layer insulation layer, the interconnection layers, and the
metal barrier layer with the sloped profile; and patterning the
second conductive layer to form metal lines, wherein the second
etching process comprises a dry etching process using a main etch
gas for physically etching the metal barrier layer and an
additional gas for chemically etching the metal barrier layer.
2. The method of claim 1, wherein the first etching process and the
second etching process comprise blanket dry etching processes in a
plasma etching apparatus using an inductively coupled plasma (ICP)
as a plasma source.
3. The method of claim 1, wherein the second etching process
comprises etching at a bias power ranging from approximately 15 W
to approximately 300 W.
4. The method of claim 1, wherein the openings are one of contact
holes and via holes.
5. The method of claim 1, wherein forming the metal barrier layer
includes forming the metal barrier layer from a material selected
from titanium nitride, titanium, and a combination thereof.
6. The method of claim 5, wherein forming the first conductive
layer comprises forming a layer of tungsten.
7. The method of claim 5, wherein forming the second conductive
layer comprises forming a layer of aluminum.
8. The method of claim 1, wherein the first etching process and the
second etching process are performed in-situ in an etching
apparatus using the same plasma source.
9. The method of claim 1, wherein the first etching process and the
second etching process are performed ex-situ in etching apparatuses
using different plasma sources.
10. A method for fabricating a semiconductor device, comprising:
forming an inter-layer insulation layer on a substrate; forming
openings in the inter-layer insulation layer; forming a titanium
nitride (TiN) layer on the inter-layer insulation layer and in the
openings; forming a tungsten layer on the TiN layer and filled in
the openings; performing a first etching process to etch the
tungsten layer to form tungsten plugs in the openings, wherein the
tungsten plugs are formed completely inside the openings and at a
depth from a top of the openings; performing a second etching
process on portions of the TiN layer exposed after the first
etching process to obtain a sloped profile of the TiN layer at top
lateral portions of the openings, the sloped profile of the TiN
layer having a rounded cusp; forming an aluminum layer on the
inter-layer insulation layer, the tungsten plugs, and the TiN layer
with the sloped profile; and patterning the aluminum layer to form
metal lines, wherein the second etching process comprises a dry
etching process using a main etch gas for physically etching the
TiN layer and an additional gas for chemically etching the TiN
layer.
11. The method of claim 10, wherein the etch gas comprises Ar, the
additional gas comprises Cl.sub.2, and the bias power ranges from
approximately 150 W to approximately 300 W.
12. The method of claim 11, wherein a flow of the Ar gas is
approximately 100 scam to approximately 1,000 scam and a flow of
the Cl.sub.2 gas is approximately 5 scam to approximately 50
sccm.
13. The method of claim 10, wherein the TiN layer serves as a metal
barrier layer.
14. The method of claim 10, wherein the first etching process uses
a main etch gas selected from the group consisting of CF.sub.4,
SF.sub.6 and NF.sub.3.
15. The method of claim 10, wherein the first etching process uses
the CF.sub.4 gas as the main etch gas and oxygen gas as the
additional gas.
16. The method of claim 15, wherein the first etching process and
the second etching process comprise blanket dry etching processes
in an etching apparatus using an inductively coupled plasma (ICP)
as a plasma source.
17. The method of claim 16, wherein the first etching process and
the second etching process are performed in-situ in an etching
apparatus using an ICP as a plasma source.
18. The method of claim 13, wherein the first etching process and
the second etching process are performed ex-situ at etching
apparatuses using different plasma sources.
Description
RELATED APPLICATION
The present application claims the benefits of priority to Korean
patent Application No. KR 2005-36591, filed in the Korean Patent
Office on Apr. 30, 2005, the entire contents of which are
incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to a method for fabricating a
semiconductor device; and, more particularly, to a method for
fabricating a semiconductor device with a metal line.
DESCRIPTION OF RELATED ARTS
As semiconductor devices are highly integrated, the design rule
also decreases. An opening burial technique, which is essential for
forming multi-layer interconnections, is needed to allow mass
production of semiconductor devices with deep openings such as
contact holes and via holes having sizes of a sub-half micron with
a high level of reliability. An example of an opening burial
technique is the tungsten plug process, because tungsten has a low
resistivity.
FIGS. 1A to 1C are cross-sectional views illustrating a method for
forming a metal line in a semiconductor device using a conventional
tungsten plug process.
Referring to FIG. 1A, an inter-layer insulation layer 12 is formed
on a substrate 11 and planarized thereafter. Substrate 11 comprises
silicon and may include other elements such as gate structures and
bit lines. Inter-layer insulation layer 12 is selectively etched to
form contact holes 13 in which metal lines are to be formed.
Contact holes 13 expose predetermined portions of substrate 11,
such as source and drain regions. A metal barrier layer 14 is
formed in contact holes 13 and on inter-layer insulation layer 12.
Metal barrier layer 14 is formed of TiN or Ti/TiN. A tungsten layer
15 is formed on metal barrier layer 14 and fills contact holes
13.
Referring to FIG. 1B, a blanket dry etching process is performed on
tungsten layer 15 using a fluorine based plasma in an inductively
coupled plasma (ICP) etching apparatus, thereby forming tungsten
plugs 15A in contact holes 13. For instance, SF.sub.6 plasma may be
used for etching tungsten layer 15. Tungsten layer 15 is over
etched by the blanket dry etching process so that tungsten plugs
15A are completely isolated from each other. More specifically,
tungsten layer 15 is etched such that the tungsten formed outside
contact holes 13 and a portion of the tungsten in contact holes 13
are etched. As a result, tungsten plugs 15A are formed at a depth
`D` from the top of contact holes 13, as shown in FIG. 1B. By
forming tungsten plugs 15A at a depth inside contact holes 13, an
electric short between subsequently formed aluminum-based metal
lines may be prevented. Reference numeral 15B denotes an
indentation formed after the above over-etching process.
Referring to FIG. 1C, a metal liner layer 16 and an aluminum layer
17 are sequentially formed on the resultant structure shown in FIG.
1B. Metal liner layer 16 is formed of Ti/TiN. Although not
illustrated, a subsequent metal line process is performed on
aluminum layer 17 to form metal lines. Because aluminum has a poor
step-coverage and indentations 15B have a very steep and vertical
profile, voids `V` occur at indentations 15B of tungsten plugs 15A
when the metal lines are formed from aluminum layer 17. Such voids
`V` may cause an electromigration event in the aluminum-based metal
lines due to electric stress. Electromigration may further result
in defects in the aluminum-based metal lines and tungsten plugs,
and may deteriorate reliability of semiconductor devices. Such
deterioration is worse when the semiconductor devices operate at
high speed, because an electric stress level and an occurrence of
the electric stress increase.
Such problems associated with tungsten plugs and aluminum-based
metal lines also occur when other forms of interconnections
including contact plugs and metal lines are formed.
SUMMARY
The present invention provides a method for fabricating a
semiconductor device capable of improving device reliability by
improving a step-coverage characteristic of a metal line formed on
a bottom structure including an interconnection layer such as a
contact plug.
Consistent with embodiments of the present invention, a method for
fabricating a semiconductor device with a metal line includes
forming an inter-layer insulation layer on a substrate; forming
openings in the inter-layer insulation layer; forming a metal
barrier layer in the openings and on the inter-layer insulation
layer; forming a first conductive layer on the metal barrier layer
and filled in the openings; performing a first etching process to
etch the first conductive layer to form interconnection layers in
the openings, wherein the interconnection layers are formed inside
the openings and at a depth from a top of the openings; performing
a second etching process on portions of the metal barrier layer
exposed after the first etching process to obtain a sloped profile
of the metal barrier layer at top lateral portions of the openings;
forming a second conductive layer over the inter-layer insulation
layer, the interconnection layers and the metal barrier layer with
the sloped profile; and patterning the second conductive layer to
form metal lines.
Also consistent with embodiments of the present invention, a method
for fabricating a semiconductor device includes forming an
inter-layer insulation layer on a substrate; forming openings in
the inter-layer insulation layer; forming a titanium nitride (TiN)
layer on the inter-layer insulation layer and in the openings;
forming a tungsten layer on the TiN layer and filled in the
openings; performing a first etching process to etch the tungsten
layer to form tungsten plugs in the openings, wherein the tungsten
plugs are formed completely inside the openings and at a depth from
a top of the openings; performing a second etching process on
portions of the TiN layer exposed after the first etching process
to obtain a sloped profile of the TiN layer at top lateral portions
of the openings; forming an aluminum layer on the inter-layer
insulation layer, the tungsten plugs, and the TiN layer with the
sloped profile; and patterning the aluminum layer to form metal
lines.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features of the present invention will become
better understood with respect to the following description of
embodiments given in conjunction with the accompanying drawings, in
which:
FIGS. 1A to 1C are cross-sectional views illustrating a method for
a semiconductor device with metal lines using a conventional
tungsten plug process;
FIGS. 2A to 2E are cross-sectional views illustrating a method for
fabricating a semiconductor device with metal lines consistent with
embodiments of the present invention;
FIG. 3 is a cross-sectional view illustrating a blanket dry etching
process consistent with a first embodiment of the present
invention;
FIG. 4 is a cross-sectional view illustrating a blanket dry etching
process consistent with a second embodiment of the present
invention;
FIG. 5 is a cross-sectional view illustrating a blanket dry etching
process consistent with a third embodiment of the present
invention; and
FIG. 6 is a cross-sectional view illustrating a blanket dry etching
process consistent with a fourth embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Methods for fabricating a semiconductor device with a metal line
consistent with embodiments of the present invention will be
described in detail with reference to the accompanying
drawings.
FIGS. 2A to 2E are cross-sectional views illustrating a method for
fabricating a semiconductor device with metal lines consistent with
embodiments of the present invention.
Referring to FIG. 2A, an inter-layer insulation layer 22 is formed
on a substrate 21. Substrate 21 comprises silicon and may include
previously formed elements such as gate structures and bit lines.
Inter-layer insulation layer 22 is patterned using a
photolithography process and a dry etching process to thereby form
openings 23 exposing predetermined portions of substrate 21, e.g.,
source and drain regions. Openings 23 can be contact holes or via
holes. Contact holes will be filled with conductive material for
providing connections between a substrate and a metal line, between
a bit line and a substrate, or between a substrate and a storage
node. Via holes will be filled with conductive material for
providing connections between metal lines. The conductive material
filled into a via hole may be referred to as a via.
A cleaning process is performed to remove a native oxide layer or
etch remnants remaining on the bottom surface of openings 23. The
cleaning process is carried out by dipping the resulting structure
shown in FIG. 2A into a solution of sulfuric acid (H.sub.2SO.sub.4)
for approximately 5 minutes and then a diluted solution of fluoric
acid (HF) for approximately 90 seconds. The HF solution is diluted
in a diluting agent at a ratio of approximately 200 parts of the
diluting agent to approximately 1 part of HF.
Referring to FIG. 2B, a metal barrier layer 24 is formed in
openings 23 and on inter-layer insulation layer 22. Metal barrier
layer 24 includes Ti/TiN or TiN and has a thickness ranging from
approximately 100 .ANG. to approximately 200 .ANG.. A first
conductive layer 25 is formed on metal barrier layer 24 and filled
in openings 23. First conductive layer 25 comprises tungsten.
Referring to FIG. 2C, first conductive layer 25 is etched to form
interconnection layers 25A in openings 23. Interconnection layers
25A can be contacts, contact plugs, plugs, or vias. To form
interconnection layers 25A, a portion of first conductive layer 25
disposed outside the openings 23 is etched using a blanket dry
etching process. Hereinafter, this blanket dry etching process is
referred to as "first blanket dry etching process."
If first conductive layer 25 comprises tungsten, the first blanket
dry etching process may be an etching using fluorine-based plasma
in an inductively coupled plasma (ICP) etching apparatus. The
fluorine-based plasma can be SF.sub.6 plasma, which etches tungsten
easily.
The first blanket dry etching over etches first conductive layer 25
so that interconnection layers 25A are isolated from each other. As
a result of the over etching, first conductive layer 25 is etched
to a depth in openings 23, and indentations 25B are formed.
Indentations 25B have a sidewall 25C at nearly 90 degrees with
respect to substrate 21. The reason for the over etch is that, if a
portion of first conductive layer 25 remains outside the openings
23 after the first blanket dry etching, that portion of first
conductive layer 25 may continue to exist even after a subsequent
etching process for forming metal lines and may cause an electric
short between the metal lines to be formed. For example, if first
conductive layer 25 comprises tungsten and a second conductive
layer for forming the metal lines comprises aluminum, and the
second conductive layer is etched using Cl.sub.2 plasma, the
tungsten in the portion of first conductive layer 25 remaining
after the first blanket dry etching still remains after the etching
of the aluminum layer because tungsten has a low etching rate under
Cl.sub.2 plasma. As a result, the aluminum-based metal lines may be
short connected by the remaining tungsten.
Then, with reference to FIG. 2D, an additional blanket dry etching
process is performed in the same or different plasma etching
apparatus where the first blanket dry etching process is performed.
Hereinafter, this additional blanket dry etching process will be
referred to as "second blanket dry etching process."
The second blanket dry etching process etches metal barrier layer
24 such that the top lateral portions of openings 23 have sloped
profile 25D. A reference numeral `R` refers to a rounded cusp of
the sloped profile 25D, and the process of rounding the cusp will
be described later. The second blanket dry etching process can be
performed at various process conditions, which will be described in
detail with reference to FIGS. 3 to 6.
Referring to FIG. 2E, a metal liner layer 26 including TiN and Ti
formed in sequential order is formed over the resulting structure
shown in FIG. 2D, and a second conductive layer 27 is formed on
metal liner layer 26. Because of sloped profile 25D of openings 23,
second conductive layer 27 can be formed with an improved
step-coverage and without voids. Although not illustrated, second
conductive layer 27 is patterned to form metal lines. Second
conductive layer 27 includes aluminum, and the etching of second
conductive layer 27 uses Cl.sub.2 plasma.
With reference to FIGS. 3 to 6, the second blanket dry etching
process will be described in detail. Through FIGS. 3 to 6,
reference numerals 44, 45, 45A, 45B, and 45D represent a metal
barrier layer including TiN (hereinafter referred to as "TiN
layer"), a first conductive layer including tungsten (hereinafter
referred to as "tungsten layer"), an interconnection layer
(hereinafter referred to as "tungsten plug"), an indentation of the
tungsten plug 45A, and a sloped profile of the indentation 45B,
respectively. The same reference numerals denoted in FIG. 2D are
used for the same elements in FIGS. 3 to 6.
Also, it is assumed that the first blanket dry etching process and
the second blanket dry etching process are performed in-situ in an
ICP plasma etching apparatus using an ICP as a plasma source. The
first blanket dry etching process and the second blanket dry
etching process can also be performed ex-situ in different plasma
etching apparatuses using different plasma sources.
FIG. 3 is a diagram illustrating a blanket dry etching process as
the second blanket dry etching process consistent with a first
embodiment of the present invention.
The first blanket dry etching process is performed to etch tungsten
layer 45 to form tungsten plugs 45A, and the second blanket dry
etching process is performed to etch TiN layer 44 so that the edges
of indentations 45B (i.e., the top lateral portions of openings 23)
have a sloped profile 45D. As mentioned above, the first blanket
dry etching process and the second blanket dry etching process can
be performed in situ in the same ICP plasma etching apparatus. The
first blanket dry etching process employs a fluorine-based gas as a
main etch gas. The fluorine-based gas is selected from the group
consisting of SF.sub.6, CF.sub.4 and NF.sub.3. When the CF.sub.4
gas is used, oxygen is additionally used. The second blanket dry
etching process can be performed using boron trichloride
(BCl.sub.3) gas as a main etch gas and with a bias power of higher
than approximately 150 W, e.g., in a range between 150 W and
approximately 300 W. The BCl.sub.3 gas flows in an amount of
approximately 50 sccm to approximately 500 sccm.
The second blanket dry etching process etches TiN layer 44 and
exposes tungsten plugs 45A. A portion of TiN layer 44 disposed
outside openings 23 is removed using the BCl.sub.3 gas. Also, a
portion of TiN layer 44 on top lateral portions of openings 23 is
etched to have sloped profile 45D.
The etching of TiN layer 44 by the second blanket dry etching
process using the BCl.sub.3 gas and the high bias power will be
described in more detail hereinafter. As a reference, a dry etching
process can be either a physical etching, or a chemical etching, or
a physicochemical etching. A physical etching is a method of
etching a target layer physically by implanting positive ions of a
plasma, which is generated by employing an inert gas such as Ar, He
or Xe, onto a wafer. A chemical etching is a method of etching a
target layer chemically using activated neutral radicals of a
plasma, which are generated by employing a gas that chemically
reacts with the target layer in a plasma state. A physicochemical
etching is a method of etching a target layer both physically and
chemically using strong collision energy, which is generated by
implanting positive ions of a plasma onto a wafer, and radicals,
which chemically react with the target layer, at the same time. A
physicochemical etching can increase an etch rate by approximately
1 .ANG. per second as compared to either physical or chemical
etching.
It is well known in the art that TiN can be chemically etched by
Cl.sub.2 gas and physically etched by boron ions. When BCl.sub.3
gas is used to etch TiN, the chlorine included in BCl.sub.3 may
chemically etch TiN and the boron included in BCl.sub.3 may
physically etch TiN. Thus, the second blanket dry etching process,
which uses BCl.sub.3 as the main etch gas, consistent with the
first embodiment, can etch TiN layer 44 both physically and
chemically so that sloped profile 45D can be formed.
In more detail of the physicochemical etching of TiN layer 44,
chlorine contained in the BCl.sub.3 gas causes a chemical etching
of TiN layer 44, whereas boron contained in the BCl.sub.3 gas
causes a physical etching of TiN layer 44. If the physical etching
occurs using only boron, TiN layer 44 disposed outside openings 23
can be removed; however, TiN layer 44 disposed on the top lateral
portions of openings 23 cannot be etched. Hence, sloped profile 45D
cannot be obtained.
If the physical etching occurs using only chlorine, TiN layer 44
disposed on the top lateral portions of openings 23 can be
isotropically etched to thereby obtain sloped profile 45D; however,
TiN layer 44 disposed outside the openings 23 cannot be etched.
Hence, an electric short event may occur due to remnants of TiN
layer 44.
Therefore, the BCl.sub.3 gas is used in the second blanket dry
etching process to provide sloped profile 45D at the top lateral
portions of openings 23 and simultaneously remove TiN outside
openings 23. TiN layer 44 disposed outside the openings 23 is
etched by both the physical etching and the chemical etching, and
TiN layer 44 disposed on the top lateral portions of openings 23 is
etched chemically.
Also, a bias power of higher than approximately 150 W, e.g., in a
range between approximately 150 W to approximately 300 W, can
increase the sputtering effect, which makes it easier to form
sloped profile 45D at the top lateral portions of the openings
23.
The second blanket dry etching process exposes inter-layer
insulation layer 22 and tungsten plugs 45A. However, inter-layer
insulation layer 22 formed of an oxide and tungsten plugs 45A are
not etched by the second blanket dry etching process due to the low
etching rates of inter-layer insulation layer 22 and tungsten plugs
45A.
Due to the sputtering effect of the second blanket dry etching
process, edge portions of inter-layer insulation layer 22 exposed
after the etching of TiN layer 44 at the top lateral portions of
openings 23 may also be etched, and thus, a cusp of sloped profile
45D can be rounded. The rounding of the cusp of sloped profile 45D
can improve the step coverage of a second conductive layer to be
deposited later.
FIG. 4 is a diagram illustrating a blanket dry etching process as
the second blanket dry etching process consistent with a second
embodiment of the present invention.
The first blanket dry etching process is performed to etch tungsten
layer 45 to form tungsten plugs 45A, and the second blanket dry
etching process is performed to etch TiN layer 44 so that the edges
of indentations 45B (i.e., the top lateral portions of openings 23)
have a sloped profile 45D. As mentioned above, the first blanket
dry etching process and the second blanket dry etching process can
be performed in the ICP plasma etching apparatus. The first blanket
dry etching process employs a fluorine-based gas as a main etch
gas. The fluorine-based gas is selected from the group consisting
of SF.sub.6, CF.sub.4 and NF.sub.3. When the CF.sub.4 gas is used,
oxygen is additionally used. The second blanket dry etching process
can be performed using BCl.sub.3 gas as a main etch gas with a bias
power of higher than approximately 150 W, e.g., in a range between
150 W and approximately 300 W. Consistent with the second
embodiment, Cl.sub.2 gas may be added to increase efficiency of the
chemical etching. A flow of BCl.sub.3 may be approximately 50 sccm
to approximately 500 sccm, and a flow of Cl.sub.2 may be
approximately 5 sccm to approximately 50 sccm. In an aspect, the
flow of Cl.sub.2 is approximately one tenth the flow of BCl.sub.3
to avoid a risk that the chemical etching is performed excessively
on the sloped profile 45D. If the chemical etching is performed
excessively, the depth of sloped profile 45D can increase beyond an
intended level, causing an over-etching of TiN layer 44 disposed on
the top lateral portions of openings 23.
The second blanket dry etching process etches TiN layer 44 and
exposes tungsten plugs 45A. A portion of TiN layer 44 disposed
outside contact holes 23 is removed using the BCl.sub.3 gas and the
Cl.sub.2 gas. A portion of TiN layer 44 disposed on top lateral
portions of openings 23 is also etched to have sloped profile
45D.
In the second blanket dry etching process, both the Cl.sub.2 gas
and the chlorine in the BCl.sub.3 gas etch TiN layer 44 chemically
and the boron in the BCl.sub.3 gas etches TiN layer 44 physically.
The addition of Cl.sub.2 increases the chemical etching rate of TiN
layer 44.
If the physical etching occurs using only boron, TiN layer 44
disposed outside openings 23 can be removed; however, TiN layer 44
disposed on the top lateral portions of the openings 23 cannot be
etched. Hence, the sloped profile 45D cannot be obtained.
If the physical etching occurs using only chlorine, TiN layer 44 on
the top lateral portions of openings 23 can be isotropically etched
to form sloped profile 45D; however, TiN layer 44 disposed outside
openings 23 cannot be etched. Hence, an electric short event may
occur due to the remnants of TiN layer 44.
In the second blanket dry etching process consistent with the
second embodiment, the Cl.sub.2 gas is added to the BCl.sub.3 gas
to form sloped profile 45D at the top lateral portions of openings
23 and at the same time TiN outside openings 23 is removed. The
BCl.sub.3 gas causes the physicochemical etching of TiN layer 44,
and the Cl.sub.2 gas is added to increase an etching rate of the
chemical etching of TiN layer 44. As a result, an etching time can
be shortened, and the shortened etching time can further result in
an elimination of an unnecessary over-exposure of the structure
beneath TiN layer 44 during the second blanket dry etching process.
Also, a bias power of higher than approximately 150 W, e.g.,
between approximately 150 W to approximately 300 W, can increase
the sputtering effect to thereby form sloped profile 45D easily at
the top lateral portions of openings 23.
The second blanket dry etching process using the BCl.sub.3 gas and
the Cl.sub.2 gas exposes inter-layer insulation layer 22 and
tungsten plugs 45A. However, inter-layer insulation layer 22 formed
of an oxide and tungsten plugs 45A are not etched during the second
blanket dry etching process due to the low etching rates of
inter-layer insulation layer 22 and tungsten plugs 45A.
Due to the sputtering effect of the second blanket dry etching
process, edge portions of inter-layer insulation layer 22 exposed
after the etching of TiN layer 44 at the top lateral portions of
openings 23 may also be etched, and thus, a cusp of sloped profile
45D can be rounded. The rounding of the cusp of sloped profile 45D
can improve the step coverage of a second conductive layer to be
deposited later.
FIG. 5 is a diagram illustrating a blanket dry etching process as
the second blanket dry etching process consistent with a third
embodiment of the present invention.
The first blanket dry etching process is performed to etch tungsten
layer 45 to form tungsten plugs 45A, and the second blanket dry
etching process is performed to etch TiN layer 44 so that the edges
of indentations 45B (i.e., the top lateral portions of openings 23)
have a sloped profile 45D. As mentioned above, the first blanket
dry etching process and the second blanket dry etching process can
be performed in the ICP plasma etching apparatus. The first blanket
dry etching process employs a fluorine-based gas as a main gas. The
fluorine-based gas is selected from the group consisting of
SF.sub.6, CF.sub.4 and NF.sub.3. When the CF.sub.4 gas is used,
oxygen is additionally used. The second blanket dry etching process
consistent with the third embodiment uses argon (Ar) gas as a main
etch gas and is performed in the ICP etching apparatus. A bias
power of higher than approximately 150 W, e.g., between 150 W and
approximately 300 W, is supplied. A flow of the Ar gas is
approximately 100 sccm to approximately 1,000 sccm.
The second blanket dry etching process etches TiN layer 44 and
exposes tungsten plugs 45A. A portion of TiN layer 44 disposed
outside contact holes 23 is removed using the Ar gas. A portion of
TiN layer 44 disposed on top lateral portions of openings 23 is
also etched to have sloped profile 45D.
Consistent with the third embodiment, plasma generated from the Ar
gas, together with the high bias power, etches TiN layer 44 to form
sloped profile 45D. Such an etching is a physical etching. The bias
power of higher than approximately 150 W, e.g., between
approximately 150 W to approximately 300 W, enhances the sputtering
effect, which can make it easier to form sloped profile 45D. Hence,
the second blanket dry etching process consistent with the third
embodiment utilizes a reinforced physical etching of the Ar gas and
the high bias power combined. As a reference, if the physical
etching is carried out using only the Ar gas but without high bias
power, TiN layer 44 disposed on the top lateral portions of
openings 23 cannot be etched, and thus, it is difficult to obtain
the sloped profile 45D.
Consistent with the third embodiment, the physical etching is
carried out using the Ar gas as the main etch gas, coupled with the
high bias power, so that sloped profile 45D is formed at the top
lateral portions of openings 23. At the same time, the portion of
TiN layer 44 disposed outside openings 23 is removed
completely.
The second blanket dry etching process consistent with the third
embodiment exposes inter-layer insulation layer 22 and tungsten
plugs 45A. However, inter-layer insulation layer 22 and tungsten
plugs 45A are not etched due to the low etching rates of
inter-layer insulation layer 22 and tungsten plugs 45A.
Due to the sputtering effect, edge portions of inter-layer
insulation layer 22 exposed after the etching of TiN layer 44 at
the top lateral portions of openings 23 may also be etched, and
thus, a cusp of sloped profile 45D can be rounded. The rounding of
the cusp of the sloped profile 45D can improve the step coverage of
a second conductive layer to be deposited later.
FIG. 6 is a diagram illustrating a blanket dry etching process as
the second blanket dry etching process consistent with a fourth
embodiment of the present invention.
The first blanket dry etching process is performed to etch tungsten
layer 45 to form tungsten plugs 45A, and the second blanket dry
etching process is performed to etch TiN layer 44 so that the edges
of indentations 45B (i.e., the top lateral portions of openings 23)
have a sloped profile 45D. As mentioned above, the first blanket
dry etching process and the second blanket dry etching process can
be performed in the ICP plasma etching apparatus. The first blanket
dry etching process employs a fluorine-based gas as a main etch
gas. The fluorine-based gas is selected from the group consisting
of SF.sub.6, CF.sub.4 and NF.sub.3. When the CF.sub.4 gas is used,
oxygen is additionally used. The second blanket dry etching process
uses Ar gas as a main etch gas. Consistent with the fourth
embodiment, Cl.sub.2 gas is added to stimulate a chemical etching.
A bias power of higher than approximately 150 W, e.g., between 150
W and approximately 300 W, is supplied. A flow of the Ar gas is
approximately 100 sccm to approximately 1,000 sccm, and a flow of
the Cl.sub.2 gas is approximately 5 sccm to approximately 50 sccm.
In an aspect, a flow of the Cl.sub.2 gas is approximately one
twentieth the flow of the Ar gas to avoid a risk that the chemical
etching is performed excessively on sloped profile 45D. If the
chemical etching is performed excessively, the depth of sloped
profile 45D can increase beyond an intended level, causing an
over-etching of TiN layer 44 disposed on the top lateral portions
of openings 23. The addition of a small amount of the Cl.sub.2 gas
can increase the depth of sloped profile 45D, and reduce an overall
etching time of the second blanket dry etching process.
The second blanket dry etching process consistent with the fourth
embodiment uses the Ar gas and the Cl.sub.2 gas to etch TiN layer
44 and to expose tungsten plugs 45A. A portion of TiN layer 44
disposed outside contact holes 23 and a portion of TiN layer 44
disposed on the top lateral portions of openings 23 are etched to
have the sloped profile 45D.
Consistent the fourth embodiment, the second blanket dry etching
process uses the gas mixture of the Ar gas and the Cl.sub.2 gas so
that TiN layer 44 can be etched chemically by the Cl.sub.2 gas. The
addition of the Cl.sub.2 gas shortens the etching time of TiN layer
44.
Consistent with the fourth embodiment, the second blanket dry
etching process physicochemically etch TiN layer 44 using the Ar
gas as the main etch gas and the added Cl.sub.2 gas. Particularly,
to obtain the sloped profile 45D at the top lateral portions of
openings 23 and to completely remove TiN layer 44 disposed outside
openings 23, the second blanket dry etching process is performed
such that TiN layer 44 disposed outside the openings 23 is etched
physically and chemically with a high etch rate and TiN layer 44
disposed on the top lateral portions of openings 23 is etched
chemically.
Also, the bias power of higher than approximately 150 W, e.g.,
between approximately 150 W to approximately 300 W, can enhance the
sputtering effect to thereby obtain the sloped profile 45D easily
at the top lateral portions of openings 23.
The second blanket dry etching process is performed using the Ar
gas and the Cl.sub.2 gas to expose inter-layer insulation layer 22
and tungsten plugs 45A. However, inter-layer insulation layer 22
formed of an oxide material and tungsten plugs 45A are not etched
due to the low etching rates of inter-layer insulation layer 22 and
tungsten plugs 45A.
Due to the sputtering effect, edge portions of inter-layer
insulation layer 22 exposed after the etching of TiN layer 44
disposed on the top lateral portions of openings 23 may also be
etched. Thus, a cusp of the sloped profile 45D can be rounded. The
rounding of the cusp of the sloped profile 45D can improve the step
coverage of a second conductive layer to be deposited later.
As discussed above, consistent with embodiments of the present
invention, a step coverage of metal lines can be improved by
forming sloped edges of indentations, which are formed on top of
interconnection layers, on which the metal lines are to be formed.
The improved step coverage can further improve the reliability of
the semiconductor devices.
While the present invention has been described with respect to
certain preferred embodiments, it will be apparent to those skilled
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention as
defined in the following claims.
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